Noise suppressor

ABSTRACT

A noise suppressor device for absorbing pulsating fluids is disclosed. A noise suppressor device has a housing which defines an axially extending bore. A resilient bladder is coaxially positioned in the bore. A spool assembly is coaxially positioned within the bladder. The spool assembly has an inner spool layer and an outer spool layer which coaxially surrounds the inner spool layer. The inner spool layer and outer spool layers each define a plurality of perforations extending therethrough. The perforations in the outer spool layer are offset from the perforations in the inner spool layer such that a direct line of sight through the first perforations and second perforations is prevented.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of application Ser. No. 08/703,647 filedAug. 27, 1996.

TECHNICAL FIELD

The present invention relates to a fluid impulse dampener, or noisesuppressor. In particular, the present invention relates to a noisesuppressor has an improved bladder design and bladder support spool.

The present invention is especially useful in suppressing noise invarious hydraulic systems. In preferred embodiments, the noisesuppressor is positioned in the hydraulic system near a pump outlet.

BACKGROUND OF THE INVENTION

Noise suppressors are used in various hydraulic systems to compress ordampen the pulses of fluid which are flowing and pulsing through thehydraulic system. The pulses (or changes in fluid pressure) in the fluidflow cause noise and wear on hydraulic systems. One type of noisesuppressor comprises a housing having a pressure chamber defined betweena flexible bladder and an interior surface of the housing. A pressurizedgas is supplied to the pressure chamber. The interior of the bladderdefines a fluid receiving chamber. The bladder is coaxially positionedover a tubular support or spool in the chamber. The support has radiallyextending perforations or holes. The fluid chamber receives the flow offluid moving through the hydraulic system. The compressibility of thepulsed fluid is achieved as the fluid passes through the fluid chamberas follows: the peak of pulsing fluid passes out through the holes inthe support and pushes against the bladder. The bladder expands into thepressure chamber. The pressurized gas on the opposite side of thebladder exerts a counter force on the bladder, thus minimizing ordampening the peak of the fluid pulse. The gas pressure pushes or actsagainst the bladder causing the bladder to be forced against the supportspool. The pulsations of the fluid passing through the housing areabsorbed or dampened in the fluid chamber due to the deflections(expansions and contractions) of the bladder and a consequentcompression of the gas present in the pressure chamber.

The noise suppressor housings must also be adequately sealed towithstand the normal gas charge pressures, which are typically in therange of approximately 50 to about 80% of operating pressure. Thepulsations of the fluid cause the bladder to expand and contract and thebladder moves in the housing. In the past, it has been difficult toadequately seal the bladder in the housing of the noise suppressor sothat fluid does not leak from the edges of the bladder into the gaspressure chamber and/or from the noise suppressor housing.

in addition, in currently used bladder-type noise suppressors, thenormal gas charge pressures and the high temperatures of the fluidspassing through the noise suppressors cause damage to the bladder. Thebladder is under constant expansion and contraction pressures. Portionsof the bladder come into repeated contact with the support stool. Thebladder wears out at the areas on the bladder where the bladder contactsthe spool. Portions of the bladder are removed from these contact areasdue to the highly repetitive nature of the pulsing cycles the fluidflowing through the noise suppressor. In particular, the portions of thebladder adjacent the holes in the spool are prematurely worn ortorn-away. That is, the edges of the holes in the spool wear away at thebladder causing the bladder to prematurely wear out and fail.

Previous attempts to prevent damage to the bladder have included theU.S. Pat. No. 4,759,387 which placed a helical wave band between a spooland a diaphragm. However, the diaphragm was still subject to undue wear.Other attempts include U.S. Pat. No. 4,628,964 which used a supportingcylinder comprised of a plurality of wire nets over a reinforcingcylinder. However, these previous attempts do not have sufficientdurability needed in many types of hydraulic systems and the helicalbands and wire nets tend to deform over time due to repeated exposure topulsing fluids, thereby decreasing the effectiveness of the noisesuppressors.

Therefore, there is a need for a noise suppressor which overcomes theabove-described drawbacks and which has increased durability.

DISCLOSURE OF THE INVENTION

The present invention is directed to an improved noise suppressor. Thepresent invention reduces wear on hydraulic system and is easilyinstalled in existing hydraulic systems.

The noise suppressor has a longitudinally housing which defines anaxially extending bore. A bladder is coaxially positioned in the bore.The bladder is supported within the bore by a spool assembly. Inpreferred embodiments, the bladder is made of an elastic material suchas a durable EPR or rubber-type material which results in extremely longservice life and requires minimal servicing.

The spool assembly is coaxially positioned within the bladder. The spoolassembly is preferably a spool type device which defines alongitudinally extending bore. The bore in the spool assembly receivesthe fluid flowing through the hydraulic system. When pulses or changesin fluid pressure occur, the spool assembly provides a means for thefluid to flow into the bladder cavity.

The spool assembly of the present invention comprises an inner spoollayer and an outer spool layer which is coaxially positioned over theinner spool layer. In a preferred embodiment, the inner and outer spoollayers are comprised of a suitably strong material such as corrosionresistant metals. In especially preferred embodiments, the inner spoollayer comprises an aluminum alloy while the outer spool layer comprisesa stainless steel material.

The inner spool layer defines a plurality of first openings orperforations which extend radially from an inner surface to an outersurface of the inner spool layer. In a preferred embodiment, the innerspool layer has a plurality of evenly spaced perforations extendingtherethrough which define a first pattern. The perforations in the innerspool layer provide sufficient openings for the pulsating fluid to flowinto the bladder. In certain embodiments, the perforations in the innerspool layer are in communication with axially oriented fluid flow pathson an outer surface of the inner spool layer. The fluid flow pathscircumferentially extend around the outer surface of the inner spoollayer and are in communication with the perforations extending throughthe outer spool layer.

The outer spool layer defines a plurality of second openings orperforations which extend radially from an inner surface to an outersurface of the outer spool layer. In a preferred embodiment, the outerspool layer comprises a material having a preferred thickness which isless than the thickness of the inner spool layer. Also, in a preferredembodiment, the outer spool layer has a plurality of the evenly spacedsecond perforations which define a second pattern, which second patternis different from the first pattern of the first perforations in theinner second layer. The second pattern of perforations in the outerspool layer is staggered so that the second perforations in the outerspool layer do not coincide with the first perforations in the innerspool layer. That is, in the preferred embodiments, there is not adirect line of sight through the second perforations in the outer spoollayer and the first perforations in the inner second layer. The secondperforations in the outer spool layer are adjacent at least a portion ofthe fluid flow paths of the inner spool layer.

The present invention is specifically directed to an improved spoolassembly having two coaxial layers of perforated support material with anarrow gap in between the layers. The perforations in each layer areoffset or staggered such that the fluid flows from perforations in onelayer, through the gap and out of the perforations in the other layer.The two adjacent layers of the spool assembly are of a design whichreduces wear on the bladder.

In certain embodiments, the internal diameter of the perforations in theinner spool layer is the same as the diameter of the perforations in theouter spool layer. It is within the contemplated scope of the presentinvention that the perforations in the inner spool layer and theperforations in the outer spool layer can have a substantiallycylindrical shape. In certain embodiments, the perforations in at leastthe outer spool layer can have a tapered or frustoconical shape.

An additional advantage is that it is now possible to provide a noisesuppressor device which can have interchangeable spool sub-assemblies.The interchangeability of the spool sub-assemblies allows the noisesuppressor device to be customized for the end user, while stillallowing the manufacturer of the noise suppressor device to maintain areduced inventory of specific noise suppressor devices. Further, it isnow possible to provide the end use customer with a more specific noisesuppressor device especially a tailored to meet the requirements of theend user.

Therefore, one object of the present invention is to provide a noisesuppressor device having improved noise dampening characteristics.

It is further object of the invention to provide an improved noisesuppression device having a spool assembly which provides an increaseduseful life to the resilient bladder in the noise suppressor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a first embodiment of a noisesuppressor device.

FIG. 2 is a cross-sectional view showing an enlargement of a portion ofFIG. 1, showing no, or an equilibrium of, pressure of fluid against oneside of a bladder and pressure of gas on an opposing side of thebladder.

FIG. 3 is a cross-sectional view, similar to FIG. 2, but showing lesserpressure of fluid against a bladder than pressure of gas on an opposingside of the bladder.

FIG. 4 is a cross-sectional view showing an enlargement of a perforationin an outer spool layer of a spool assembly.

FIG. 5 is a cross-sectional view showing a different embodiment of anoise suppressor device showing no, or an equilibrium, of pressure fluidagainst one side of a bladder and pressure of gas on an opposing side ofthe bladder.

FIG. 6 is a cross-sectional view, similar to FIG. 5, but showing lessorpressure of fluid against a bladder than pressure of gas on an opposingside of the bladder.

BEST MODE OF CARRYING OUT INVENTION

FIG. 1 generally shows a noise suppressor device 10 comprising a housing12, a generally hollow flexible bladder 14, and a spool assembly 16. Thebladder 14 is coaxially positioned within a longitudinally extendingbore 18 in the housing 12. The spool assembly 16 is coaxially positionedwithin the bladder 14. The shape of the longitudinally extending bore 18through the housing 12 is defined by an inner surface 19 of the housing12. The inner surface 19 and the bladder 14 define a pressure chamber 20while the hollow bladder 14 and the spool assembly 16 define a fluidchamber 22.

The housing 12 further comprises a charging port 24 which defines aradially extending bore 26 for receiving a high pressure charging valve28, shown in phantom. The radially extending bore 26 is in communicationwith the pressure chamber 20. A supply of a gas, such as nitrogen, isintroduced under pressure to the pressure, chamber 20.

The longitudinally extending bore 18 of the housing 12 has a first end30 having a first interior surface 32 and a second end 34 having asecond interior surface 36. The interior surfaces 32 and 36 engaginglyreceive the spool assembly 16. The housing 12 further defines a firstgroove or detent 42 for receiving a first end 44 of the bladder 14 and asecond groove or detent 46 for receiving a second end 48 of the bladder14.

The noise suppressor device 10 further includes a first adapter 50axially positioned within the first end 30 of the housing 12 and asecond adapter 50' axially positioned within the second end 34 of thehousing 12.

In the embodiment shown, the first adapter 50 comprises a first end 52which is positioned adjacent the bladder 14 when the adapter 50 is inposition in the housing 12 and a second, opposing end 53 which isexternal to the housing 12 for receiving a hose or other coupling means,not shown. The first adapter 50 has an exterior surface 54 whichincludes a threaded portion 56 located between the first end 52 and thesecond end 53. The threaded portion 56 engages a corresponding threadedportion 58 on the interior surface 32 of the first opening 30. The firstadapter 50 further includes a detent or groove 60 whichcircumferentially extends around the exterior surface 54. The detent orgroove 60 receives a packing or sealing member 62, such as an O-ring andwasher 63, for sealing the first adapter 50 into the opening 30 of thehousing 12.

The first end 52 of the adapter 50 can have an angled or sloped surfaceto readily engage the first end 44 of the bladder 14. The first end 52and the exterior surface 54 of the first adapter 50 secure the first end44 of the bladder 14 in the detent 42 of the housing 12.

The first adapter 50 has an interior surface 70 which defines a flangeportion 74. The interior surface 70 of the first adapter 50 axiallyreceives the spool assembly 16. In a preferred embodiment, the spoolassembly 16 is held in position against the interior surface 70 of thefirst adapter 50. In certain embodiments, a packing or sealing member 76is positioned adjacent the interior flange portion 74 to secure thespool assembly 16 within the first adapter 50.

The noise suppressor device 10 further includes the second adapter 50'which is axially positioned within the second end 34 of the housing 12.In the embodiment shown, the first adapter 50 and the second adapter 50'have substantially the same shape or configuration; however, it is to beunderstood that it is within the contemplated scope of the presentinvention that the first adapter 50 and the second adapter 50' can havedifferently shaped configurations to allow for the installation ofdifferent couplings or hoses on the distal ends 53 and 53' of the firstadapter 50 and second adapter 50', respectively.

In the embodiment shown, the second adapter 50' comprises a first end52' which is positioned adjacent the bladder 14 when the second adapter50' is in position in the housing 12 and a second, opposing end 53'which is external to the housing 12 for receiving a hose or othercoupling means, not shown. The second adapter 50' has an exteriorsurface 54' which includes a threaded portion 56' located between thefirst end 52' and the second end 53'. The threaded portion 56' engages acorresponding threaded portion 58' on the interior surface 36 of thesecond opening 34. The second adapter 50' further includes a detent orgroove 60' which circumferentially extends around the exterior surface54'. The detent or groove 60' receives a packing or sealing member 62',such as an O-ring and washer 63', for sealing the second adapter 50'into the second opening 34 of the housing 12.

The first end 52' of the second adapter 50' can have an angled or slopedsurface to readily engage the second end 48 of the bladder 14. The firstend 52' and the exterior surface 54' of the second end 50' secure thesecond end 48 of the bladder 14 in the second detent 46 of the housing12.

The second adapter 50' has an interior surface 70' which defines aflange portion 74'. The interior surface 70' of the second adapter 50'also axially receives the spool assembly 16. In a preferred embodiment,the spool assembly 16 is held in position against the interior surface70' of the second adapter 50'. In certain embodiments, a packing orsealing member 76' is positioned adjacent the interior flange 74' tosecure the spool assembly 16 within the second adapter 50'.

The spool assembly 16 comprises an inner spool layer 80 and an outerspool layer 90. The inner spool layer 80 is coaxially positioned withinthe bladder 14. The inner spool layer 80 has a first end 82 which isadjacent the first adapter 50 and a second end 82' which is adjacent thesecond adapter 50'. The first end 82 and second end 82' are held inposition against the sealing members 74 and 74', respectively. The innerspool layer 80 has an outer surface 84 and an inner surface 86.

A plurality of radially oriented first perforations 88 extend throughthe inner spool layer 80 from the outer surface 84 to the inner surface86. The perforations 88 are preferably evenly spaced along at least acenter portion 89 of the inner spool layer 80. The perforations 88 arearranged in a first pattern on the inner spool layer 80. In a preferredembodiment, the perforations 88 in the center portion 89 begin at apoint adjacent the first end 52 of the first adapter 50 and terminate ata point adjacent the second end 52' and the second adapter 50'. Thegenerally evenly spaced perforations 88 on the inner spool layer 80provides sufficient openings for changes in fluid pressure to passthrough the perforations 88.

The inner surface 86 of the inner spool layer 80 defines an axiallyextending bore 87. The axially extending bore 87 is sealed from theinterior chamber 20 by the first end 44 and second end 48 of the bladder14.

The outer spool layer 90 comprises a first end 92 which is adjacent thefirst adapter 50 and a second end 92' which is adjacent the secondadapter 50'. The outer spool layer 90 is coaxially positioned on theinner spool layer 80 and is positioned between the bladder 14 and theinner spool layer 80. The outer spool layer 90 has an outer surface 94and an inner surface 96.

A plurality of radially oriented second perforations 98 extend throughthe outer layer 90 from the outer surface 94 to the inner surface 96.The perforations 98 are preferably evenly spaced along the outer spoollayer 90. The perforations 98 are arranged in a second pattern on theouter spool layer 90. The generally evenly spaced perforations 98 on theouter spool layer 90 provides sufficient openings for changes in fluidpressure to pass through the perforations 98.

In certain embodiments, the spool assembly 16 further comprises a firstspacer 100 which is coaxially positioned adjacent the first end 92 ofthe outer spool layer 90 and a second spacer 100' coaxially positionedadjacent the second end 92' of the outer spool layer 90. It is to beunderstood however, that the present invention is also useful with onespacer positioned adjacent at least one of the ends of the outer spoollayer.

In a preferred embodiment, the inner spool layer 80 defines a firstspecified thickness or width between the outer surface 84 and the innersurface 86 and the outer spool layer 90 defines a second specifiedthickness or width between the outer surface 94 and the inner surface96. In a preferred embodiment, the thickness or width of the inner spoollayer 80 is greater than the thickness or width of the outer spool layer90.

The perforations 98 in the outer spool layer 90 define a predeterminedor specified pattern such that the perforations 98 are in a staggeredconfiguration with respect to the perforations 88 in the inner spoollayer 80. The perforations 98 extend through the outer spool layer 90such that each perforation 98 is adjacent a portion of the inner spoollayer 80. The perforations 88 extend through the inner spool layer 80such that each perforation 88 is adjacent a portion of the outer spoollayer 90. The perforations 88 and 98 are offset, as can be best seen inFIG. 2, such that there is no direct line of sight through the innerspool layer 80 and the outer spool layer 90 along a line perpendicularto the plane of the outer surface 94 of the outer spool layer 90.

In a preferred embodiment, the perforations 88 in the inner spool layer80 define a first, specified diameter and the perforations 98 in theouter spool layer 90 define a second specified diameter. In certainpreferred embodiments, the outer spool layer 90 has a thickness rangingfrom about 0.008 to about 0.03 inches while the inner spool layer 80 isapproximately 2-4 times thicker than the outer spool layer 90. The outerspool layer 90 is coaxially positioned over the inner spool layer 80such that a small gap 110 or clearance exists between the outer spoollayer 90 and the inner spool layer 80. The gap 110 defines a fluid flowpath for the fluid. The gap 110 is preferably less than the thickness ofthe outer spool layer 90.

In a preferred embodiment, the width of the gap 110 ranges from about0.0005 to about 0.0035 inches. The gap 110 provides a tortuous path forthe fluid to flow from the axial bore 87 through the perforations 88,through the gap 110, through the perforations 98, and finally contactingthe bladder 14. In operation, any fluid flowing through the noisesuppressor device 10 will substantially fill the gap 110 between theouter spool layer 90 and inner spool layer 80.

When fluid flows through the axial bore 87 in the inner spool layer 80,the fluid also flows through the perforations 88 in the inner spoollayer 80, through the gap 110, and through the perforations 98 in theouter spool layer 90. The fluid contacts the bladder 14 causing thebladder 14 to expand or distend into the pressure chamber 20. The gaspressure on the bladder 14 keeps the bladder 14 from expanding too farduring peak or pulse periods of fluid passing through the axial bore 87.The gas in the pressure chamber 20 is compressed, thus dampening orabsorbing the forces of the pulsing fluid.

As shown in FIG. 3, when a trough or low pulse of fluid passes throughthe axial bore 87, the bladder 14 is pushed by the gas pressure radiallyagainst the outer surface 94 of the outer spool layer 90. Portions 112of the bladder 14, under pressure from the gas in the, pressure chamber20, extend into the gap 110 between the outer spool layer 90 and theinner spool layer 80. The portions 112 of the bladder 14 contact theouter surface 84 of the inner spool layer 80. Further radial movement ordistortion of the bladder 14 is prevented by the outer surface 84. Theinner spool layer 80 acts to prevent the material comprising the bladder14 from being sheared off. The offset or staggered configuration of theperforations 98 and 88 prevent the bladder 14 from being extruded toofar.

In certain embodiments, the perforations 98 in the outer spool layer 90can have a countersink-type configuration to further prevent damage tothe bladder 14. FIG. 4 shows an enlargement of a perforation 98 in oneembodiment of an outer spool layer 90. It is to be understood however,that the perforation 98 can have other configurations and theconfiguration shown in FIG. 4 provides one example of a suitable shapefor a perforation 98. The perforation 98 comprises a first portion 120which extends from the inner surface 96 of the inner spool layer 90 in adirection toward the outer surface 94. The first portion 120 has a firstinterior diameter 122. The first portion 120 is generally perpendicularto a plane defined by the inner surface 96. The perforation 98 defines asecond portion 124 which is in coaxial alignment with the first portion120. The second portion 124 extends from the first portion 120 to theouter surface 94 of the outer spool layer 90. The second portion 124 hasa second interior diameter 126 which is greater than the first interiordiameter 122 of the first portion 120. The second portion 124 has agenerally tapered or frustoconical shape, as defined by at least oneside wall 128. The second portion 124 defines a countersink-type shapewhich, in certain preferred embodiments, has an approximately 90° angleas defined by the side wall 128. The second portion 124 further preventsshearing or tearing of the bladder 14 when the bladder 14 is pulledagainst the outer spool layer 90.

Another embodiment of a spool assembly 116 is shown in FIGS. 5-6. It isto be understood that the spool assembly 116 is positioned in the noisesuppressor device 10 in substantially the same manner as the embodimentshown in FIGS. 1-3, and that, for the sake of ease of illustration, thehousing of the noise suppressor device is not shown in FIGS. 5-6.

The spool assembly 116 comprises an inner spool layer 180 and an outerspool layer 190. The inner spool layer 180 is coaxially positionedwithin the bladder 114. The inner spool layer 181 has an outer surface184 and an inner surface 186. The inner surface 186 of the inner spoollayer 180 defines an axially extending bore 187.

A plurality of radially oriented perforations 188 extend through theinner spool layer 180 from the outer surface 184 to the inner surface186. The perforations 188 are preferably evenly spaced along at least acenter portion 189 of the inner spool layer 180. The perforations 188are arranged in a first pattern on the inner spool layer 180. Thegenerally evenly spaced perforations 188 on the inner spool layer 180provide sufficient openings for changes in fluid pressure to passthrough the perforations 188.

The outer spool layer 190 is coaxially positioned on the inner spoollayer 180 and is positioned between the bladder 114 and the inner spoollayer 180. The outer spool layer 190 has an outer surface 194 and aninner surface 196.

A plurality of radially oriented perforations 198 extend through theouter layer 190 from the outer surface 194 to the inner surface 196. Theperforations 198 are preferably evenly spaced along the outer spoollayer 190. The perforations 198 are arranged in a second pattern on theouter spool layer 190. The generally evenly spaced perforations 198 onthe outer spool layer 190 provide sufficient openings for changes influid pressure to pass through the perforations 198.

In a preferred embodiment, the inner spool layer 180 defines a firstthickness or width between the outer surface 184 and the inner surface186, and the outer spool layer 190 defines a second thickness or widthbetween the outer surface 194 and the inner surface 196. In a preferredembodiment, the thickness or width of the inner spool layer 180 isgreater than the thickness or width of the outer spool layer 190.

The perforations 198 in the outer spool layer 190 define the first,predetermined pattern such that the perforations 198 are in a staggeredconfiguration with respect to the perforations 188 in the inner spoollayer 180. The perforations 198 extend through the outer spool layer 190such that each perforation 198 is adjacent a first portion of the fluidflow path of the inner spool layer 180.

The perforations 188 extend through the inner spool layer 180 such thateach perforation 188 is adjacent a portion of the outer spool layer 190.The perforations 188 and 198 are offset, as can be best seen in FIG. 5,such that there is no direct line of sight through the inner spool layer180 and the outer spool layer 190 along a line perpendicular to theplane of the outer surface 194 of the outer spool layer 190.

The outer surface 184 of the inner spool layer 180 defines a pluralityof axially oriented fluid flow paths 202. In the embodiment shown inFIGS. 5 and 6, each fluid flow path 202 is adjacent and in communicationwith a corresponding first perforation 188. Each fluid flow path 202circumferentially extends around the outer surface 184 of the innerspool layer 180. In the embodiment shown in FIGS. 5 and 6, the fluidflow path 202 has a first portion 204 and a second portion 206. Thefirst portion 204 of the fluid flow path 202 is adjacent and coaxialwith the perforation 188 in the inner spool layer 180. In a preferredembodiment, the first portion 204 has an axially extending length alongthe outer surface 184 which is longer than the diameter of theperforation 188.

The second portion 206 of the fluid flow path 202 is adjacent and incommunication with the first portion 204. The second portion 206 is alsoadjacent and in communication with the perforation 198 in the outerspool layer 190. In a preferred embodiments, the second portion 206 hasan axially extending length along the outer surface 184 which extends atleast to a point beyond the perforation 198 in the outer spool 190.

In the embodiment shown in FIGS. 5 and 6, the inner spool layer 180includes fluid flow paths 202 which are adjacent and in communicationwith each perforation 188. However, it should be understood that it iswithin the contemplated scope of the present invention, that onlycertain perforations 188 can be in communication with a fluid flow path.For the sake of explanation and illustration, however, the embodimentshown herein has a fluid flow path adjacent and in communication witheach perforation in the inner spool layer.

In a preferred embodiment, the perforations 188 in the inner spool layer180 define a first, specified diameter and the perforations 198 in theouter spool layer 190 define a second specified diameter. In certainpreferred embodiments, the outer spool layer 190 has a thickness rangingfrom about 0.008 to about 0.03 inches while the inner spool layer 180 isapproximately 2-4 times thicker than the outer spool layer 190. Theouter spool layer 190 is coaxially positioned over the inner spool layer180 such that a gap 210 or clearance exists between the outer spoollayer 190 and the inner spool layer 180.

The width of the gap 210 between the inner spool layer 180 and the outerspool layer 190 varies. In a preferred embodiment, the width of the gap210 at the points A, between the inner spool layer 180 and the outerspool layer 190 where there is no fluid flow path 202, ranges from about0.0005 to about 0.0035 inches.

The width of the gap 210 at points B, adjacent the second portion 206 ofthe fluid flow path 202 and the perforations 198 in the outer spoollayer 190, ranges from about 0.005 to about 0.007 inches. The gap 210provides a tortuous pathway for the fluid to flow from the axial bore187 through the perforations 188, through the first portions 204 and thesecond portions 206 of the fluid flow paths 202, through the gap 210,through the perforations 198, and finally contacting the bladder 114. Inoperation, the fluid flowing through the noise suppressor device willsubstantially fill the fluid flow path 202 and the gap 210 between theouter spool layer 190 and inner spool layer 180.

When the fluid flows through the axial bore 187 in the inner spool layer180, the fluid also flows through the perforations 188 in the innerspool layer 180, through the fluid flow path 202, through the gap 210,and through the perforations 198 in the outer spool layer 190. The fluidcontacts the bladder 114 causing the bladder 114 to expand or distendinto the pressure chamber (not shown). The gas pressure on the bladder114 keeps the bladder 114 from expanding too far during peak or pulseperiods of fluid passing through the axial bore 187. The gas in thepressure chamber is compressed, thus dampening or absorbing the forcesof the pulsing fluid.

As shown in FIG. 5, when a trough or low pulse of fluid passes throughthe axial bore 187, the bladder 114 is pushed by the gas pressureradially against the outer surface 194 of the outer spool layer 190.Portions 212 of the bladder 114, under pressure from the gas in thepressure chamber, extend into the gap 210 between the outer spool layer190 and the inner spool layer 180. The portions 212 of the bladder 114contact the second portions 206 of the fluid flow paths 202 of the innerspool layer 180. Further radial movement or distortion of the bladder114 is prevented by the second portions 206. The inner spool layer 180acts to prevent the material comprising the bladder 114 from beingsheared off. The offset or staggered configuration of the perforations198 and 188 prevent the bladder 114 from being extruded too far. At thesame time, however, the perforations 198 and 188 and the fluid flowpaths 202 allow the fluid to quickly and easily flow into and out of thebladder 114.

While the invention has been described in terms of various preferredembodiments, the skilled artisan will appreciate the variousmodifications and substitutions, omissions and changes which may be madewithout departing from the spirit thereof. Accordingly, it is intendedthat the scope of the present invention be defined solely by the scopeof the following claims including the equivalents thereof.

We claim:
 1. A noise suppressor device comprising:a housing defining an axially extending bore through which pressurized fluid flows; a bladder coaxially positioned in the bore; a spool assembly coaxially positioned in the bladder, the spool assembly consisting of an inner spool layer and an outer spool layer which axially surrounds the inner spool layer, the inner spool layer having radially oriented first perforations extending therethrough, the first perforations being in communication with axially oriented fluid flow paths circumferentially extending around an outer surface of the inner spool layer, the outer spool layer having radially oriented second perforations extending therethrough; and the first perforations extending through the inner spool layer defining a first pattern and the second perforations extending through the outer spool layer defining a second pattern, the first perforations in the inner spool layer are nonaligned from the second perforations in the outer spool layer, wherein a direct line of sight through the first perforations and second perforations is prevented and wherein the second perforations in the outer spool layer are in communication with the fluid flow paths in the inner spool layer, and wherein an unobstructed gap is defined between the inner spool layer and the outer spool layer, the gap defining a tortuous path between the first perforations in the inner spool layer and the second perforations in the outer spool layer.
 2. The noise suppressor device of claim 1, wherein the first perforations in the inner spool layer have a first diameter and the second perforations in the outer spool layer have a second diameter, the first diameter of the first perforations in the inner spool layer being substantially the same diameter as the second diameter of the second perforations in the outer spool layer.
 3. The noise suppressor device of claim 1, wherein the inner spool layer comprises an aluminum alloy and the outer spool layer comprises a stainless steel material.
 4. The noise suppressor device of claim 1, wherein the housing has a first end for receiving a first adapter and a second end for receiving a second adapter, the first and second adapters securing the bladder in the housing.
 5. The noise suppressor device of claim 4, wherein the inner spool layer has a first end secured in the first adapter and a second end secured in the second adapter.
 6. The noise suppressor device of claim 1, wherein the first perforations in the inner spool layer and the second perforations in the outer spool layer each define a generally cylindrical shape.
 7. The noise suppressor device of claim 1, wherein the second perforations in the outer spool layer have a first cylindrical portion in coaxial alignment with a frustoconical shape portion.
 8. The noise suppressor device of claim 7, wherein the frustoconical portion of the second perforations is defined by an angled wall having an interior angle of approximately 90°.
 9. The noise suppressor device of claim 1, wherein the fluid flow path includes a first portion which is adjacent and coaxial with the first perforation and a second portion which is adjacent and in communication with the first portion of the fluid flow path and which is further adjacent and in communication with the second perforation in the outer spool layer.
 10. The noise suppressor of claim 9, wherein a portion of the gap between the second portion of the fluid flow path and the outer spool layer ranges from about 0.005 to about 0.007 inches.
 11. The noise suppressor device of claim 1, wherein the bladder and the housing define a pressure chamber which is pressurized to counteract the forces exerted on the bladder by the pressurized fluid flow.
 12. The noise suppressor device of claim 1, wherein the gap defined between the inner spool layer and the outer spool layer is less than the thickness the outer spool layer. 